Coping saws, sometimes referred to as scroll saws, are well known as manually reciprocating tools for cutting through thin materials such as plywood, masonite, balsa wood, plastic and soft metals. A conventional coping saw blade has perpendicular pins at each end that engage slots in anchor bolts at the tips of a U-frame. The U-frame has an aperture at one tip for an anchor bolt with a head and an aperture at the other tip for an anchor bolt with a thread for attaching a handle and tensioning the blade between the two tips of the U-frame. U.S. Pat. No. 4,095,635 to Hutchins is an example of an improved blade holding system using the conventional blade with pins at the ends and anchor bolt slots.
The blade is customarily mounted with the blade cutting surface away from the tips of the U-frame. However, as disclosed in Hutchins, the anchor bolts can be rotated in the apertures to change the direction of the cutting surface of the blade.
The depth of the U-frame determines the dimension that a cut can be made inside from the edge of material to be cut. By rotating the blade 90 degrees by the anchor bolts, a second cut can be made parallel to that same edge. By rotating the blade an additional 90 degrees by the anchor bolts, a third cut can be made to return to the edge of the material resulting in the separation of a rectangular piece of material. The kerf of these cuts will be the thickness of the saw blade.
The rotation of the saw blade by the anchor bolts enables a user to obtain smooth cuts but it requires stopping the sawing motion to rotate the handle to relieve the tension on the blade so that the blade can be rotated via the anchor bolts to the desired angle. The handle is then rotated to re-tension the blade and sawing motion resumed. This is considered to be inconvenient, time consuming and increases the wear on the threaded handle and anchor bolt interface.
U.S. Pat. No. 1,548,393 to Strug is an earlier effort to permit a rotary adjustment of a coping saw blade to any desired angle to the workpiece by an adjustment of ratchet wheels with leaf springs intersecting the teeth of the ratchet wheels. Again, the sawing motion in Strug must be stopped to permit the angular adjustment as in Hutchins.
U.S. Pat. No. 2,514,609 to Roy is an effort to permit multi-directional coping saw cutting without interrupting the sawing motion. Roy discloses a blade with teeth extending continuously and spirally in a helical manner around a hardened cylindrical wire body. The kerf of the cut is the diameter of the wire plus the additional extending teeth depth. The cutting action is more of a ripping action with the teeth not aligned with a thin backing support resulting in a cut that is not as smooth and thin as a conventional coping saw cut.
U.S. Pat. No. 3,642,038 to Mannes is another effort to permit multi-directional cutting in a sabre saw in which the user is not limited to the depth of a U-frame as in a coping saw because the blade is only connected at one end. However, in Mannes as in Roy, the cutting action is a ripping action and the kerf is not very thin and smooth.
It is an object of the present invention to provide a saw blade that can be used in a coping saw U-frame to provide a smooth cut in multiple directions without changing the setting of the blade and without changing the orientation of the saw. This is accomplished by an axial movement of the saw blade that will rotate the cutting surface 90 degrees each in three increments resulting in four different cutting directions. Within each increment, the cutting surface permits enough reciprocating movement to perform a conventional smooth and thin cut.
It is a further object of the present invention to provide rubber O-rings to secure anchoring pins in the anchor bolts to prevent broken blades from being propelled when a blade breaks and the spring tension of the U-frame is released.
It is a further object of the present invention to provide a coping saw that is safe, convenient to use and requiring less time to use by children in handicraft classes where they can develop manual dexterity and coordination in using prescribed sawing motion and axial adjustment to achieve desired directional cutting changes.
It is a further object of the invention to provide a coping saw that is an improvement over Hutchins, Strug, Roy and Mannes, incorporated herein by reference, in the features of those prior art saws as explained above.